This invention relates to a system for monitoring the relative proximity between aircraft within a given area, and more particularly to the provision of visual indication to operators of individual aircraft of the proximity of other aircraft, in order to avoid mid-air collision.
Ever-increasing air traffic congestion, especially in the vicinity of air traffic control areas in large metropolitan regions, has led to increasing concern over the danger of in-flight collision. It is well recognized that in poor visibility conditions, i.e., in the presence of clouds, fog, haze or the like, it is difficult if not impossible to observe other aircraft in one's vicinity. However, even with optimum visibility conditions, one may not be aware of the presence of other aircraft in potentially dangerous locations, because of both the large number of aircraft visible and the high degree of concentration required for other matters when entering a high-density air traffic area.
It has heretofore been the exclusive province of air traffic controllers to "take command" in such high-volume air traffic areas, leaving little discretion to the individual aircraft operators, and hence shifting the responsibility for avoiding collision. Nevertheless, discretion is still vested in individual operators to the extent necessary to avoid imminent danger.
However, with ever-increasing air traffic congestion, errors or omissions are possible on the part of the controller, not to mention the possibility of lack of complete clarity in communications between the controller and the aircraft operator. For example, although the controller's normal function is to decide upon and indicate courses and altitudes to the aircraft in his control area, on occasion he may be required to give oral warning to two or more aircraft which have strayed into dangerous proximity to one another. It is, perhaps, in this latter case that the danger of misinterpretation of these communications becomes most significant. One of the involved aircraft operators may misunderstand or misinterpret the warning, e.g., by continuing on his course in the belief that he has identified and avoided the aircraft in respect to which the warning was given, when in fact the danger still exists.
Various solutions have been proposed to some of the foregoing problems, however, the solutions heretofore proposed have been difficult to implement or have given rise to yet other problems. One such proposal has been to provide various alarm buzzers or other such indications to the pilots of aircraft in time to take evasive action. Unfortunately, however, in a high-traffic area, it is most difficult to set such devices so as to give adequate warning, while at the same time avoiding constant disturbance by sounding of the alarm mechanisms in view of the normal close proximity of aircraft in such areas. Additionally, the demands for attention of the pilot of a modern aircraft are quite significant already, without requiring attention to yet further alarms or the like. As a further matter, many of such systems exhibit great disadvantage in their relative complexity and expense. In this regard, these systems generally require all aircraft to be similarly equipped with such complex and expensive equipment in order for the system to function adequately, yet in view of the expense of such systems, many aircraft would not be so equipped.
Accordingly, it is believed that significant shortcomings of the prior art are the complexity and expense of proposed systems; the failure of such proposals to make use of already available techniques and systems to the maximum extent possible, and the probability that many operators of private aircraft would not purchase the expensive apparatus required for the workability of the proposed systems. In high-traffic areas, such systems cannot work to the advantage of commercial aviation, if private, non-commercial aircraft are not included within the system automatically, at least to the extent of being observable in some form.